JAVA EE: Java Tutorial : Java IO (Java RandomAccessFile

Wednesday 23 November 2016

Java Tutorial : Java IO (Java RandomAccessFile - V3)

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Java Tutorial : Java IO (Java RandomAccessFile - V3)

myfile.txt

John visits to india.

RandomAccessFileReadDemo.java

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;

public class RandomAccessFileReadDemo
{
    public static void main(String[] args) throws IOException
    {
        RandomAccessFileReadDemo randomAccessFileReadDemo = new RandomAccessFileReadDemo();
        byte[] byteArray = randomAccessFileReadDemo.readFromFile("myfile.txt",15);
        System.out.println(new String(byteArray));
    }

    private byte[] readFromFile(String fileName, int position)
            throws FileNotFoundException, IOException
    {
        RandomAccessFile randomAccessFile = null;
        byte[] byteArray;
        try
        {

            randomAccessFile = new RandomAccessFile(fileName, "r");

            /*
             * Sets the file-pointer offset, measured from
             * the beginning of this file, at which the next
             * read or write occurs.
             */
            randomAccessFile.seek(position);

            byteArray = new byte[5];
            randomAccessFile.read(byteArray);
        }
        finally
        {
            if (randomAccessFile != null)
            {
                randomAccessFile.close();
            }
        }
        return byteArray;
    }

}

Output

india

RandomAccessFileWriteDemo.java

import java.io.IOException;
import java.io.RandomAccessFile;

public class RandomAccessFileWriteDemo
{
    public static void main(String[] args) throws IOException
    {
        RandomAccessFileWriteDemo randomAccessFileWriteDemo = new RandomAccessFileWriteDemo();
        randomAccessFileWriteDemo.writeToFile("myfile.txt", " and USA", 20);
    }

    private void writeToFile(String fileName, String data, int position)
            throws IOException
    {

        RandomAccessFile randomAccessFile = null;
        try
        {
            randomAccessFile = new RandomAccessFile(fileName, "rw");

            /*
             * Sets the file-pointer offset, measured from
             * the beginning of this file, at which the next
             * read or write occurs.
             */
            randomAccessFile.seek(position);
            randomAccessFile.write(data.getBytes());
            System.out.println("Successfully written to the file.");
        }
        finally
        {
            if (randomAccessFile != null)
            {
                randomAccessFile.close();
            }
        }
    }

}